Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$148.47	10.531%	$164.1054	$164.11	$164.10	$164.10
Purchase #2	$43.74	13.316%	$49.5644	$49.56	$49.55	$49.60
Purchase #3	$128.49	12.812%	$144.9521	$144.95	$144.95	$145.00
Purchase #4	$41.41	3.836%	$42.9985	$43.00	$43.00	$43.00
Purchase #5	$71.85	6.636%	$76.618	$76.62	$76.60	$76.60
Purchase #6	$92.40	9.174%	$100.8768	$100.88	$100.90	$100.90
Purchase #7	$207.71	11.583%	$231.769	$231.77	$231.75	$231.80
7 purchase totals =	$734.07		$810.8842	$810.89	$810.85	$811.00